I agree with Mal in that you'll be safe, but wear eye protection just in case. I've deprimed live primers on my Dillon 550 without setting them off I don't think doing it on a single stage would be any more likely to do it.
If you do it on a progressive make sure there is no powder in the hopper or primers in the primer tube (or whatever your particular brand uses) just in case one does get set off.
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